Biodegradable adhesive packaging

ABSTRACT

A method and composition of packaging an adhesive composition, especially a thermoplastic or thermosetting hot melt adhesive. The method comprises the steps of providing one substantially uniform separate portion of the adhesive composition; sufficiently solidifying said portion for packaging; and substantially completely surrounding said sufficiently solidified portion with a biodegradable polymeric packaging material. The packaging material being meltable together with the adhesive composition and blendable into said molten adhesive composition, the kind and amount of said biodegradable packaging material being chosen so as not to disadvantageously affect the properties of the adhesive composition when blended into the molten adhesive and applied to a substrate.

This is a continuation-in-part of U.S. patent application Ser. No.07/738,176, filed Jul. 30, 1991, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a method of packaging an adhesivecomposition, especially a thermoplastic or thermosetting hot meltadhesive, in a biodegradable package which doesn't separate and/ordegrade upon exposure to conditions present in the adhesive applicationequipment.

BACKGROUND OF THE INVENTION

Thermoplastic adhesives, especially hot melts, can be confectioned andpackaged as disclosed in German patent 22 48 046. Hot melt adhesive issqueeze-cut into roughly pillow-shaped pieces, the pieces aresubsequently cooled and thus solidified and are then put into sacks orcartons for packaging.

In order to reduce the tendency of the individual pillows to stick, i.e.adhere to each other, it is known to coat them with a separating,anti-stick substance, such as wax or a polymer, as shown in DE 33 27 289Kaiser. WO 84/03457 and WO 84/03468, Societe Nouvelle RaffinerieMeridionale de Ceresines-Belix, disclose a method to outwardly coatautoprotected blocks with a powdery separating agent. For thermoplasticadhesive compositions with a relatively high softening point (above 120°C. and especially above 150° C.) these coatings provide sufficientanti-stick properties. Such compositions can therefore be packaged,stored and dispensed from sacks without any major sticking problems.

Another packaging for adhesive compositions is to wrap or cast biggerportions of the adhesive in plastics film material, such as thickpolyethylene film. These known packagings have the disadvantage that thethermoplastic adhesive composition must be removed from the packagingprior to use, which means an extra handling step. Further, the packagingmaterial must be discarded after emptying, which leads to material wasteand expenditure for disposing of the used packaging material.

German patent 36 25 358 to Hausdorf discloses a method to completelywrap a single solid hot melt adhesive material block in a thermoplastic,especially a copolyamide film material with a melting point between 120°C. and 150° C., to prevent sticking of the adhesive to the internalsurfaces of a melting apparatus when pressure-melting the adhesive. Thefilm material is melted and mixed with the adhesive. This prior artcenters on copolyamide materials in view of their inherent hot meltadhesive properties. Today, application temperatures of less than 150°C., preferably in the range of 110° C. to 140° C. are required by theend user to reduce thermal degradation problems of the adhesive as wellas distortion of the substrates used. Therefore, for most applications,copolyamide films are not advantageous in view of their high meltingpoints and problems encountered in homogeneously melting and mixing suchmaterials together with customary hot melt adhesives.

U.S. Pat. No. 4,337,181 discloses film forming formulations comprisingstarch based films which can be blown into films and used asbiodegradable films.

U.S. Pat. No. 4,503,098 discloses disposable articles made from watersoluble polymers. The water soluble polymers include poly (alkyleneoxide), hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinylalcohol, polyvinyl pyrrolidone polyacrylamide, polyacrylic acid,poly(vinyl methyl ether-co-maleic anhydride) with a degradablewater-insoluble polymer selected from cyclic ester polymer, a poly βhydroxy butyrate, a dialkanoyl polymer, or an ethylene polymer.

The modes of biodegradation of plastics was studied in an articleentitled Degradable Plastics, Materials Forum (1989) 13, 1-10, M. J.Robey, G. Field and M. Styzinski. Many uses of biodegradable polymersincluding those in the medical science area were highlighted.

However, to date, there has not been a satisfactory solution proposedfor a biodegradable packaging for pillowed adhesives as described above.

There is a need in the industry for a packaging material which exhibitsbiodegradability. If such a package were available, the packaged hotmelt pillows would be opened, the hot melt pillows would be poured intothe premelt tank, and the film package could be discarded in the trashreceptacle. The spent packages would then be transported to a compostfacility. The previous films would often take years to break down intocomponents small enough to be digested by bacteria. Thus, from anenvironmental standpoint, it is advantageous to have a film whichbiodegrades as quickly as possible.

It is an object of this invention to provide an adhesive package whichis biodegradable. Biodegradability is generally defined as a productwhich breaks down and is physically and substantially consumed bymicroorganisms under conditions typically present in waste compostingprocesses.

A further problem encountered with some previous films includesnoncompatibility with the packaged adhesive when the bag is incorporatedwith the molten adhesive. Upon melting of the packaged adhesive, themolten film does not form a substantially homogeneous mixture with themolten adhesive. Thus, when the film does not become assimilated intothe adhesive, the film can separate and degrade upon heating and cancreate problems with the hot melt application equipment. By the term"degrade" it is meant an unassimilated portion of the film gels, chars,or skins upon exposure to heat. The resultant mixture can clog nozzlesand guns of hot melt application equipment. Thus, it is an importantobject of this invention to provide a film which blends into the moltenadhesive and does not gel, separate or degrade upon heating of themolten adhesive with the dissolved package.

It is a further object of this invention to limit any change inviscosity of the molten adhesive when the film mixes with the adhesive.It is critical in many applications to have minimal changes in theviscosity, and thus the bag should not adversely effect the viscosity.

To attain these and other objects and advantages, a method of packagingan adhesive composition with a biodegradable film is shown as well ascriteria for the selection of the biodegradable films.

SUMMARY OF THE INVENTION

The present invention comprises the steps of providing one substantiallyuniform separate portion of an adhesive composition; sufficientlysolidifying the portion for packaging; substantially surrounding thesufficiently solidified portion with a biodegradable plastics packagingmaterial; the material being meltable together with the adhesivecomposition and blendable into said molten adhesive composition, thekind and amount of said packaging material being chosen so as not todisadvantageously affect the properties of the adhesive composition whenblended into the adhesive and applied through application equipment.

DETAILED DESCRIPTION OF INVENTION

A plurality of plastic nets or film materials can be used according tothis invention. The plastic net or film material must be biodegradable.One test for biodegradability is a compost test. Typically, compostpiles have temperatures no more than 70° C., generally averaging 50°-60°C. and 100% relative humidity. Upon exposure times of two weeks to threemonths, products responsive to composting processes break downphysically and are substantially consumed by microorganisms. Anothertest of biodegradability is described in the Sturm test. The Sturm testor ASTM 5209 measures CO₂ evolution and is described below:

ASTM 5209 is a test method which is performed by placing a sample of thetest polymer into a flask containing sewage sludge as the bacterialsource. The test samples are inserted into a flask containing sewagesludge. Through this flask, air containing no CO₂ is passed through theflask. The CO₂ free air flows through the test flask and into a secondflask containing BA(OH)₂. Thus, any CO₂ generated in the flaskcontaining a polymer sample, via the metabolic activity of the bacteriafeeding on the polymer sample, travels to the second flask, with theresulting formation of BA(CO₃). This last flask is titrated withhydrochloric acid to determine the amount of BA(OH)₂ remaining insolution. These titrations are done about twice a week and new freshsolutions are then put into place.

The amount of carbon dioxide generated over a period of time isindicative of the rate of degradation of the polymer. An example ofacceptable CO₂ generation for polycaprolactone is a generation of 300milligrams over a 15 day period. However, the amount of CO₂ differs fordifferent polymers. Other tests of biodegradability are envisioned andcome within the scope of this invention.

The film material must also be capable of creating a homogeneous mixturewith the molten adhesive, which significantly decreases the tendency ofthe film to gel or char during application. The film should also notadversely affect the viscosity of the molten adhesive mixture. Manyadhesive systems have narrow windows of permissible viscosity change andthus the molten bag must not change the viscosity in any appreciablemanner.

A preferred film for the present invention is a polycaprolactone film.The polycaprolactone film exhibits compatibility in hot melts containingfunctionalities such as hydroxyl, acidic or other common functionalitiesexhibited in hot melt systems. By compatibility it is meant the film issubstantially miscible and does not separate from the adhesive after thepackaged adhesive is heated.

Polymers such as EVA, polyethylene, polypropylene, EMA, ENBA, ENBACO,may be blended with the polycaprolactone film. However, the additions ofsuch polymers will slow the degradation process down. In fact, forcompositions of less than about 70-80% polycaprolactone, no appreciabledegradation will occur. Tackifiers and plasticizers can be blended withpolycaprolactone. Tackifiers include rosin acids, rosin esters, terpenephenolics, acetophenone formaldehyde, as well as those stated below.Plasticizers include castor oil, epoxidized soybean oil, benzoateplasticizers, as well as those stated before.

Specific examples of polycaprolactone films include films of between 5μm and 200 μm, preferably between 15 μm and 50 μm thickness, dependingon available dispensing equipment; such films being especially usefulfor packaging low softening point adhesive composition pillows batchwiseinto, say, 5 lb. bags with subsequent compression to remove air. Morespecifically, a polycaprolactone film is cast or blown from a resinavailable under the trademark Tone®, commercially available from UnionCarbide Chemicals & Plastics Company, Inc. The polycaprolactone in blownfilm form is commercially available from Bio Industries. Otherpolycaprolactone films include those made by Interox such as Capa 650.

Other polymers useful for the present invention include copolymers ofhydroxybutyric acid and hydroxyl acid, which is made by bacteria. Arelated polymer, polyhydroxybutyrate, is also useful. Other bacteriacreated polymers may also be used, including biodegradable classes ofpolyesters made by bacteria in biosynthetic processes includingpolyhydroxybutyrate, polyhydroxy valerate and copolymers made thereof,such as Biopol®, commercially available from Imperial ChemicalIndustries. Other polymers include hydrophobic polymers such aspolylactic acid, polylactides, polycyano acrylate, polyortho esters,polyanhydrides, polyacetals, polyketals, polyamides, hydrophilicpolymers such as poly hydroxy ethyl methacrylate, polyglutamic acid,water soluble polymers such as poly vinyl pyrrolidone, polyacrylamide,poly acrylic acid, poly ethylene glycol, hydrogels such as cross-linkedpolymers of HEMA with methoxy ethylmethacrylate or methyl methacrylate,naturally occurring polymers containing starch and modified starch,cellulose and its derivatives, cross-linked proteins,syntheticpolypeptide based polymers and gelatin.

The films of the present invention need not be comprised of a 100% ofthe biodegradable polymer to come within this invention. Mixtures of thebiodegradable film of the present invention with other polymers ispermissible. Mixtures of above about 70-80% of a biodegradable polymerand remaining percent being a second or a plurality of polymers ispermissible as long as the overall film is still compatible with theadhesive. Polymers suitable for mixing include ethylene based polymerssuch as ethylene/vinyl acetate, ethylene acrylate, ethylenemethacrylate, ethylene methyl acrylate, ethylene methyl methacrylate,high and low density polyethylene, polyethylene blends and chemicallymodified polyethylene, copolymers of ethylene and 1-6 mono- ordi-unsaturated monomers, polyamides, polybutadiene rubber, polyesterssuch as polyethylene terephthalate, polybutylene terephthalate;thermoplastic polycarbonates, atactic poly-alpha-olefins, includingatactic polypropylene, and others; thermoplastic polyacrylamide,pollacrylonitrile, copolymers of acrylonitrile and other monomers suchas butadiene styrene; polymethyl pentane, polyphenylene sulfide,aromatic polyurethanes; styrene-acrylonitrile,acrylonitrile-butadiene-styrene, styrene-butadiene rubbers, polyethyleneterephthalate, acrylonitrile-butadiene-styrene elastomers, polyethylenesulfide, A-B, A-B-A, A-(B-A)_(n) -B, (A-B)_(n) -Y block copolymerswherein the A comprises a polyvinyl aromatic block, the B blockcomprises a rubbery midblock which can be partly hydrogenated, andmixtures of said substances, but other similar materials can be used aswell, to match the properties of the adhesive packaged.

The biodegradable polymers of the present invention may also be blendedwith tackifiers and plasticizers. Such tackifiers and plasticizersuseful for blending include those disclosed below.

In any case, it is advantageous to restrict the amount of packagingmaterial used to between 0.1 and 10% by weight and preferably 0.2 to0.5% with respect to the weight of the adhesive composition contained inthe package. This prevents undue dilution and corresponding modificationof the adhesives' characteristics.

The biodegradable envelope containing the discrete adhesive units ismade of a material that, when blended into the adhesive, does notsubstantially negatively influence the adhesive characteristics, andpreferably is either a component of the adhesive or is a componentphysically and chemically compatible with the adhesive in the melt priorto application. The polymer should not cause a physical phasing orseparation of the adhesive, and should not reduce adhesive properties.

HOT MELT ADHESIVE SYSTEMS

Briefly, thermoplastic synthetic resin materials used in hot meltadhesives comprise a variety of polymerized material. These polymers areblended with other ingredients such as plasticizers, tackifiers andextenders, to form an adhesive. Such polymers include polyethylene,polypropylene, polyvinyl acetate, polyvinyl butyryl, polyvinylalcohol,ethylene-vinylalcohol polymers and other polyvinyl resins; polystyreneresins, A-B-A block copolymers comprising polymers wherein A is apolystyrene block and B is a rubbery midblock section, acrylic andmethacrylic acid ester resins; blocked polyesters/ethers andamides/ethers; various other materials compounded from synthetic resinssuch as polyisobutylene, polyamides, cumarone-indene products andsilicones. Such thermoplastic resins usually have permanent solubilityand fusability so that when hot, they can flow or creep under stress andsoften to some extent to form a bond. After cooling, the materialspreferably resist creep and bond deformation. They are used in themanufacture of tape, safety glass, shoe cements, for the bonding orlamination of film, foil or non-woven laminates, metals, woods, rubber,paper and many other materials.

Briefly, thermosetting resin adhesives comprise a variety ofphenol-aldehyde, urea-aldehyde, melamine-aldehyde, and othercondensation polymerization materials including polyepoxy, polyurethaneand silicone resins. Thermosetting resins are characterized by beingconverted to insoluble and infusible materials, sometimes by means ofeither heat or catalytic action. Thermosetting adhesive compositionsinclude epoxies, urethanes, silicones, phenolics, resorcinol, urea,melamine, formaldehyde, phenol-furfuraldehyde, and the like and are usedfor the bonding of wood textiles, paper, plastics, rubber, automotive,and appliance assembly and many other end uses.

Briefly, the adhesives of the natural and bitumen group consist of thosemade from asphalt, shellac, rosin and its esters, and similar materials.They are typically used for bonding of various materials includingminerals, linoleum and the like.

THERMOPLASTIC POLYMERS

The thermoplastic base polymer that can be used in the manufacture ofthe novel adhesive of the invention are thermoplastic polymers that aresufficiently compatible with tackifiers, plasticizers, and otherthermoplastic or thermosetting components to form a substantialhomogeneous melt and solid. Typically in these adhesives, afterapplication, the polymer provides mechanical and cohesive strength.

Any of a variety of available thermoplastic materials can be used in thecompositions of the invention. Examples of such thermoplastics areethylene based polymers such as polyethylene and its co- andterpolymers, ethylene/vinyl acetate, ethylene acrylate, ethylenemethacrylate, ethylene methyl acrylate, ethylene methyl methacrylate,copolymers of ethylene and 1-6 mono- or di-unsaturated monomers etc.,polyamides, polybutadiene rubber, polyesters such as polyethyleneterephthalate, polybutylene terephthalate, polyester/polyether, etc.,thermoplastic polycarbonates, atactic poly-alpha-olefins, includingatactic polypropylene, and others; thermoplastic polyacrylamide,polyamide/polyether, polyacrylonitrile, copolymers of acrylonitrile andother monomers such as butadiene, styrene, etc., polymethyl pentane,polyphenylene sulfide, aromatic polyurethanes; styrene-acrylonitrile,acrylonitrile-butadiene-styrene, styrene-butadiene rubbers, polyethyleneterephthalate, acrylonitrile-butadiene-styrene elastomers, polyphenylenesulfide. Also, A-B, A-B-A, A-(B-A)_(n) -B, (A-B)_(n) -Y block copolymerswherein the A comprises a polyvinyl aromatic block, the B blockcomprises a rubbery midblock which can be partly hydrogenated, andothers can be used. The aromatic character of the polymers providescompatibility with the aromatic plasticizing agents discussed below andprovides controlled compatibility with the tackifier or the tackifierblends used to control modules in the-adhesive compositions. Thepreferred polymers should have a molecular weight sufficient that, whenused in an adhesive formulation, the adhesive can maintain a highcohesive strength.

Preferred polymers for use in the adhesives of this invention compriseEVA, APP, linear A-B-A block, linear A-(B-A)_(n) -B multiblockcopolymers, and radial or teleblock copolymers of the formula (A-B)_(n)-Y wherein A comprises a polystyrene block, B comprises a substantiallyrubbery polybutadiene or polyisoprene block, Y comprises a multivalentcompound, and n is an integer of at least 3. The midblocks can bepost-treated to improve their heat stability through hydrogenation orother post-treatment removing residual unsaturation. We believe that thesize and the amount of the A or end blocks in the A-B-A block ofcopolymer structure should be as much as 15-51 wt-% of the polymer.

While the total styrene content of the polymers can be as much as 51wt-% of the polymer, and since the polymers can have more than two Ablocks for improved performance, the largest A block should be less thanor equal to about 20 wt-% of the polymers, and, most preferably, is lessthan or equal to 15 wt-% of the polymer. In an S-B-S(styrene-butadiene-styrene) copolymer, the preferred molecular weight isabout 50,000 to 120,000, and the preferred styrene content is about 20to 35 wt-%. In an S-I-S (styrene-isoprene-styrene) copolymer, thepreferred molecular weight is about 100,000 to 150,000 and the preferredstyrene content is about 14-30 wt-%. Hydrogenating the butadienemidblocks produces rubbery midblocks that are typically considered to beethylene-butylene midblocks.

Such block copolymers are available from Shell Chemical Company,Enichem, Fina and Dexco. Multiblock or tapered block copolymers (theA-(B-A)_(n) -B type) are available from Firestone under the STEREON 840Aand 845 trademarks.

Another usable polymer is available under the trade name TUFPRENE A fromAsahi, Japan.

The adhesive compositions of the invention can contain other compatiblepolymers, fillers, pigments, dyes, oils, catalysts, inhibitors,antioxidants, UV absorbers, waxes, and other conventional additives.

TACKIFYING RESIN

The adhesives of the invention can contain a tackifying resin incombination with a thermoplastic block copolymer optionally with aplasticizer or other components.

Tackifying resins useful in the adhesives of the invention compriserosin derivatives including wood rosin, tall oil, tall oil derivatives,rosin ester resins, natural and synthetic terpenes and aliphaticaromatic or mixed aliphatic-aromatic tackifying resins. Aromaticmonomers useful in forming the aromatic containing resin compositions ofthis invention can be prepared from any monomer containing substantialaromatic qualities and a polymerizable unsaturated group. Typicalexamples of such aromatic monomers include the styrenic monomers,styrene, alphamethyl styrene, vinyl toluene, methoxy styrene, tertiarybutyl styrene, chlorostyrene, etc., indene monomers including indene,methyl indene and others. Aliphatic monomers are typical natural andsynthetic terpenes which contain C₆ and C₅ cyclohexyl or cyclopentylsaturated groups that can additionally contain a variety of substantialaromatic ring substituents. Aliphatic tackifying resins can be made bypolymerizing a feed stream containing sufficient aliphatic monomers suchthat the resulting resin exhibits aliphatic characteristics. Such feedstreams can contain other aliphatic unsaturated monomers such as1,3-butadiene, cis-1,3-pentadiene, trans-1,3-pentadiene,2-methyl-1,3-butadiene, 2-methyl-2-butene, cyclopentadiene,dicyclopentadiene, terpene monomer, terpene phenolic resins and others.Mixed aliphatic aromatic resins contain sufficient aromatic monomers andsufficient aliphatic monomers and optionally other C₃ -C₈ unsaturatedmonomers to produce a resin having both aliphatic and aromaticcharacter. The article by Davis, "The Chemistry of C₅ Resins," discussessynthetic C₅ resin technology.

Representative examples of such aliphatic resins include hydrogenatedsynthetic C₉ resins, synthetic branched and unbranched C₅ resins,synthetic branched and unbranched C₅ resins and mixtures thereof.Representative examples of such aromatic tackifying resins includestyrenated terpene resins, styrenated C₅ resins or mixtures thereof. Theselection of tackifying resins is often based on the nature of the B ormidblock radial block copolymer. Rosin derivatives are best forS-I-S/S-B-S blends and can be used with either S-I-S or S-B-S alone.Hydrogenated C₉ or straight aliphatic resins are preferred for S-I-Scopolymers. For S-B-S copolymers, styrenated terpenes or rosin estersare preferred.

The adhesive compositions of the invention can contain rosin and rosinderivatives as a tackifying agent. Rosin is a solid material that occursnaturally in the oleo rosin of pine trees and typically is derived fromthe oleo resinous exudate of the living tree, from aged stumps and fromtall oil produced as a by-product of kraft paper manufacture. After itis obtained rosin can be treated by hydrogenation, dehydrogenation,polymerization, esterification, and other post treatment processes.Rosin is typically classed as a gum rosin, a wood rosin, or as a talloil rosin which indicates its source. The materials can be usedunmodified, in the form of esters of polyhydric alcohols, and can bepolymerized through the inherent unsaturation of the molecules.Materials are commercially available and can be blended into theadhesive compositions using standard blending techniques. Representativeexamples of such rosin derivatives include pentaerythritol esters oftall oil, gum rosin, wood rosin, or mixtures thereof.

Specific examples of useful tackifying resins that can be compatiblewith a variety of thermoplastic resins or thermosetting resins used inthe adhesives of the invention include materials such as natural andmodified rosins, glycerol, and pentaerythritol esters of natural andmodified rosins, copolymers and terpolymers of natural terpenes,polyterpene resins having a softening point as determined by ASTM methodE28-58 T, of from about 80° C. to 150° C., phenolic modified terpeneresins and hydrogenated derivatives thereof; aliphatic petroleumhydrocarbon resins having a ring and ball softening point of from about70° C. to 135° C., aromatic petroleum hydrocarbon resins andhydrogenated derivatives thereof and alicyclic petroleum hydrocarbonresins and the hydrogenated derivatives thereof.

PLASTICIZERS

A plasticizer is broadly defined as a typically organic composition thatcan be added to thermoplastics, rubbers and other resins to improveextrudability, flexibility, workability, or stretchability. Typicalplasticizers in adhesives are plasticizing oils that are liquid attypical ambient temperature. The plasticizer used in the adhesives ofthe invention can also be typically a solid composition at ambienttemperature having a softening point of at least 45° C. Preferably, thesolid plasticizer is a composition with a softening point of at least60° C. Increased softening points (60°-130° C.) can aid in improvingheat resistance or preventing bond failure at high temperatures.

Plasticizing oils are used in the construction/elasticattachment/pressure sensitive adhesives of the invention. Such oils areprimarily hydrocarbon oils low in aromatic content. Preferably the oilsare paraffinic or naphathenic in character. The oils are preferably lowin volatility, are clear and have as little color and odor as possible.The use of a plasticizing oil of this invention also contemplates theuse of olefin oligomers, low molecular weight polymers, vegetable oilsand their derivatives and similar plasticizing liquids.

One useful class of plasticizers used in the invention comprises acyclo-aliphatic or aromatic ester of a benzene dicarboxylic acid. Suchplasticizers are prepared by forming an ester from a cyclo-aliphatic oraromatic alcohol such as cyclohexanol, phenol, naphthol, or othermonohydroxy alcohol compounds having from 5 to 12 carbon atoms. Theester compounds are formed from dicarboxylic acid compounds, typicallyphthalic acids. Phthalic acids that can be used in the plasticizers are1,2-benzene dicarboxylic acid, 1,3-benzene dicarboxylic acid(isophthalic acid), or 1,4-benzene dicarboxylic acid (terephthalicacid). The preferred plasticizers of this class comprise dicyclohexylphthalate or diphenyl phthalate. Most preferably, dicyclohexylorthophthalate is used.

A second class of useful plasticizers comprise an aromatic carboxylicacid ester of a polyfunctional alcohol having 1 to 10 hydroxyl groups.Polyfunctional alcohols that can be used in the compositions of thisclass of plasticizers include compounds having at least two hydroxylgroups and at least two carbon atoms in the molecule. Specific examplesof preferred hydroxy compounds include ethylene glycol, propyleneglycol, 1,2-butylene glycol, 1,4-butylene glycol, glycerine, glucose,fructose, sucrose, mannitol, trimethylol ethane, 1,4-cyclohexanedimethanol, pentaerythritol, 2,2-dimethyl-1,3-propane diol, 2-hydroxymethyl-2-methyl-1,3-propane diol, neopentyl glycol, and other usefulpolyfunctional hydroxyl compounds. Aromatic acids that can be used withthe polyfunctional alcohols to form this class ester plasticizercompounds of the invention include aromatic carboxylic acids, typicallyhaving at least one aromatic group and at least one carboxyl function.Representative acids include benzoic acid, naphthanoic acid, and4-methyl benzoic acid. Typical examples of such useful plasticizersinclude triethylene glycol tribenzoate, trimethylol ethane tribenzoate,glycerol tribenzoate, sucrose benzoate, pentaerythritol tetrabenzoate,2,2-dimethyl-1,3-propane diol dibenzoate, triethylene glycol dibenzoate,glycerol tribenzoate, 2-hydroxymethyl-2-methyl-1,3-propane dioltribenzoate, pentaerythritol tetrabenzoate, neopentyl glycol dibenzoate,mixtures thereof and others.

A preferred plasticizer is a solid with a softening point above 60° C.which belongs to the class of plasticizers including cyclohexanedimethanol dibenzoate compounds. A 1,4-cyclohexane dimethanol dibenzoate(containing cis- and trans- isomers) is exemplified and produces themaximum control over variation and change in adhesive physicalproperties.

A third class of useful plasticizers for use in the invention comprise asulfonamide class made from aromatic sulfonic acids. Such plasticizersgenerally fall within the structural formula:

    R-Ar-SO.sub.2 -NR.sub.2

wherein each R is independently selected from the group consisting ofhydrogen, aliphatic and cyclo-aliphatic radicals having 1 to 12 carbonatoms. Each R can be typically hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, tertiary butyl, ethyl hexyl, neopentyl,cyclohexyl, deodecyl etc. R is preferably methyl, ethyl or cyclohexyl.Such sulfonamide plasticizers can also be used in the form of a resinousmaterial formed through the condensation of formaldehyde with saidsulfonamide plasticizer.

We have found the A-B-A block copolymer, A-B-A-B-A-B multiblockcopolymer and radial block copolymer thermoplastic resins can be used ina variety of useful adhesives. Such adhesives are disclosed in Collins,U.S. Pat. No. 4,136,699 which teaches a particular blend of A-B-Acopolymer terpene or synthetic terpene tackifying resin and oil for usein the preparation of disposable articles. In addition, the followingadhesives can be useful in the invention:

                  TABLE I                                                         ______________________________________                                        Low Polymer Resin Compositions                                                                             Most                                                       Useful    Preferred                                                                              Preferred                                        ______________________________________                                        Plasticizing Oil                                                                          5-75        10-60    40-50                                        Tackifier   25-95       30-90    35-65                                        Polymer     0-15         0-12    0.1-10                                       ______________________________________                                    

                  TABLE II                                                        ______________________________________                                                                     Most                                                       Useful    Preferred                                                                              Preferred                                        ______________________________________                                        Solid Plasticizer                                                                          5-70       10-50    20-30                                        Tackifier   20-85       30-75    35-65                                        Polymer     10-55       12-35    15-30                                        ______________________________________                                    

                  TABLE III                                                       ______________________________________                                                                      Most                                                         Useful Preferred Preferred                                       ______________________________________                                        Radial block copolymer*                                                                      5-14     7-13      8-12                                        A-B-A block copolymer*                                                                       0-14     0-12      0-10                                        Tackifier      45-85    50-80     55-75                                       Plasticizing Oil                                                                             5-35     6-30      8-20                                        Synthetic polyethylene                                                                       0-10     0.1-9     0.25-5                                      wax (or other oil                                                             complexing agent)                                                             ______________________________________                                         *Total polymer content (including both radial block and linear block          polymer) is typically about 15 wt% or less of the adhesive.              

Such hot melt adhesive materials based on A-B-A or other types of blockcopolymers can be made into pillows and can be packaged with coextrusioncoating made from the A-B-A or other block copolymer technology. Sincethe coextruded coating will comprise from about 0.1 to about 5 wt-% ofthe total adhesive mass, the amount of block copolymer used informulating the adhesive pillow can be reduced and can be added to themelt in the form of the coextrusion coating. Such technology is taughtin U.S. Pat. Nos. 4,054,632 and 3,723,035 and is herein incorporated byreference.

One part and two part polyurethane adhesive materials can be used inpreparation of the adhesives of the invention. Such materials aredisclosed in U.S. Pat. No. 4,412,033 and 4,390,678 found in the tableset forth below.

Such adhesives rely on the reactivity between a polyol and a urethaneprepolymer wherein the isocyanate groups condense with hydroxyl groupsand prepolymer. Other types of urethane materials including hydroccuringor moisture curing urethane adhesives can be used in the invention.Additionally, two part urethane adhesives wherein the isocyanatematerial is formulated and manufactured in separate pillows from thepolyol material can be made.

Additionally, one part urethane adhesives having substantial proportionsof thermoplastic polymers can be used in the adhesives of the invention.Such adhesives are disclosed in the following tables.

                  TABLE IV                                                        ______________________________________                                                  Typical Preferred Most                                                                             Preferred                                                Adhesive                                                                              Adhesive     Adhesive                                                 Parts by                                                                              Parts by     Parts by                                                 Weight  Weight       Weight                                         ______________________________________                                        Thermoplastic                                                                             1-200     20-175       20-150                                     Polymer                                                                       Isocyanate  100       100          100                                        Terminated                                                                    Prepolymer                                                                    Tackifying Resin                                                                          1-200     20-200       40-135                                     ______________________________________                                    

In the practice of the present invention, the adhesive composition, e.g.a hot melt adhesive, is prepared by mixing polymer, synthetic or naturalresin, wax or paraffin and other substances as desired and well-known inthe art, this mixing or blending being carried out at elevatedtemperatures and by customary methods.

The adhesive composition is then pumped to an orifice for dispensing.Usually, a coating with a separating anti-stick substance will beprovided, and the coated composition will be pre-cooled prior todispensing.

In a preferred embodiment of this invention, the dispensed compositionis squeeze-cut, and thus separated into individual, pillow-shapedportion pieces. At this stage, the composition is already partlysolidified, i.e. the individual pieces are sufficiently solidified attheir outside, but they are able to be squeeze-cut and still retaintheir pillow-like shape afterwards, although the interior of the pillowsmay still be fairly hot and liquid.

The pillows are thereafter placed in a cooling bath, usually with wateras a cooling liquid and are sufficiently solidified for packaging. Atthis stage, the heat remaining in the pillows can be adjusted bysuitable choice of cooling time, to keep the pillows warm enough fordeformation in a subsequent compression step.

The sufficiently solidified pillows are now conveyed to a packagingstation, e.g. a bagging machine and are placed into nets or bags ofbiodegradable film packaging material according to this invention. Forpackaging the customary coated hot melt pillows, it is presentlypreferred to produce bags from a blown film of polycaprolactone withabout a 0.7 mil.-2.6 mil. thickness, each bag taking about 1000 grams ofpillows.

Each filled bag is then sealed by a weld seam. At this stage, the bagcontains a fairly loose filling of relatively stiff pillows and acorresponding amount of air.

If necessary, in order to reduce the initially mentioned problems insubsequent use of low softening point adhesive composition pillowspackaged according to this invention, the bag can be put in a press andcompressed as well as compacted at elevated pressure and temperature, orit can be simply stacked with other, similar bags under sufficient heat,so that the compression is effected by the weight of the stack. In thelatter case, the heat can be provided by either placing the stacks in acorrespondingly heated room or by allowing the pillows to retainsufficient internal heat in the cooling process, this heat thenresoftening the solidified outer regions of each pillow after thepackaging.

In another preferred embodiment, the hot melt adhesive will be extrudedfrom an extruder provided with suitable cooling means, the adhesivehaving a temperature of between about 50° C. and 60° C. upon extrusion.The adhesive is extruded directly into a bag or sack of the filmmaterial according to the invention. Polycaprolactone films have meltingpoints of about 60° C., thus, when using polycaprolactone extrudedadhesive should be less than about 60° C. The adhesive can be cut afterextrusion and before packaging, but preferably, the adhesive is extrudedinto the packaging bag or sack without such comminution, until thedesired amount of adhesive is received in the package. At this stage,the extruded adhesive is cut off, the package is sealed and a new bag orsack is connected to the extruder for filling.

In this embodiment, the extrusion temperature of the adhesive providessufficient plasticity and shapability of the adhesive for substantiallyuniformly filling the package, without leaving undesirable voids ordamaging the bag or sack in the filling or packaging process.

Preferred embodiments of the invention will now be described in moredetail, by reference to the following examples:

TESTING Beaker Testing

Different films were tested for their compatibility with a hot meltadhesive, HL-1295, commercially available from H. B. Fuller anddescribed in U.S. Pat. No. 5,024,667, (herein incorporated byreference). A film of polycaprolactone polyester (Tone® P787commercially available from Union Carbide), a 2.5% vinyl acetate VA film(NA 420,000 commercially available from Quantum USI), 14% methacrylateEMA film (XPE 182 available from Exxon Corp.), and 28% vinyl acetate EVAfilm (XZA 68.0 available from Consolidated Thermoplastics Company) weretested using the HL-1295 adhesive by adding 0.5 wt-% of each film to 200g samples of the hot melt. The beaker is layered with 4 equal layers ofhot melt and film. The beakers were allowed to sit in an oven at 350° F.for 96 hours. The results were as follows:

                  TABLE V                                                         ______________________________________                                        Film           Ring     Skinning  Charring                                    ______________________________________                                        Polycaprolactone                                                                             No       No        No                                          Polyester                                                                     14% Methacrylate                                                                             Yes      No        Yes                                         EMA                                                                           2.5% Vinyl     Yes      Yes       Yes                                         Acetate VA                                                                    28% Vinyl Acetate                                                                            Yes      No        Yes                                         EVA                                                                           ______________________________________                                    

A ring formed as a result of partial skinning and charring. The ring orskin appeared after 24 hours and remained the same for 96 hours. The hotmelts continued to darken. As is evident for Table V, the PCL filmexhibited no ring or skinning or charring on the surface of theadhesive. Such properties results in no unwanted gelling upon exposureto heat typically present in adhesive application equipment.

Further tests were performed as follows: 199 g of an EVA/rosin esterbased adhesive was placed in a glass beaker along with 1.0 g of thefilm. The beaker was layered with adhesive and film by placingapproximately 50 g of adhesive, and 0.25 g of film in 4 layers. Thebeaker was then placed in an oven at 350° F. (obtained from applicationtemperatures) and allowed to sit with no mixing for 72 hours.Observations were made during this time as to whether or not the filmseparated from the adhesive and whether or not the film charred orgelled. A sample of the straight adhesive with no film was used as thecontrol. The sample with the PCL showed the same performance (i.e. noskin, char or gel or separation of film) as the control. Film sampleswere tested comprising the following: a 28% VA EVA sample, a 14% MA EMAsample, and a 2.5% VA EVA. The hot melt was an opaque amber color at theoutset. No separation of the film was evident initially.

                  TABLE VI                                                        ______________________________________                                                        28%     14%                                                                   VA      MA                                                    Film   Control  EVA     EMA   2.5% VA EVA                                                                             PCL                                   ______________________________________                                        Initial                                                                              Amber    Amber   Amber Amber     Amber                                 24 hours                                                                             No skin  Ring    Ring  40% skin  No skin                               ______________________________________                                    

The 24 hour data refers to the amount of skinning that was evident foreach of the samples. A ring refers to evidence of skin and char onlyaround the edge of the beaker and not on the surface of the hot melt.The 28% VA EVA and the 14% MA EMA were better than the 2.5% VA EVA filmbut did not perform as well as the PCL which showed no difference fromthe control. The samples remained as they were after 24 hours up to 72hours when they were removed from the oven. The only changes were thatthe samples continued to darken with age.

Blended Testing

Polycaprolactone was blended in an 80% PCL to 20% polymer or resin ratiowith ethylene vinyl acetate (28% VA and 5 Melt Index which is suppliedby Quantum USI and DuPont); with ethylene methylacrylate (28% MA and 3Melt index which is XS 12.04 available from Exxon); with NA 59300polyethylene (melt index 22 from USI Chemicals Company) and with ForalAX rosin acid (available from Hercules). These samples were made intofilms. Heat stabilities were run by placing 199 g of the HL-1295adhesive and 1 g of the film in a glass beaker. The beaker is againlayered with 4 equal layers of hot melt and film. The samples wereplaced in an oven at 350° F. with no mixing and allowed to sit for 96hours. The samples are designated as follows:

#1 HL-1295 adhesive

#2 w/80% Tone P 787 and 20% EVA (28-05)

#3 w/80% Tone P 787 and 20% EMA (28-03) (XS 12.04)

#4 w/80% Tone P 787 and 20% polyethylene (NA 59300)

#5 w/80% Tone P 787 and 20% Foral AX (rosin acid)

#6 w/PCL film from Bio Industries Inc. (Tone P 787)

                  TABLE VII                                                       ______________________________________                                        #1         #2      #3      #4    #5     #6                                    ______________________________________                                        Initial                                                                              Amber   Amber   Amber Amber Amber  Amber                               24 Hours                                                                             No      No      No    Ring  No skin                                                                              No skin                                    skin    skin    skin                                                   96 Hours                                                                             No      No      No    Ring  No skin                                                                              No skin                                    skin    skin    skin                                                   ______________________________________                                    

Between 24 and 96 hours, the only changes that occurred in the adhesivewas that the color continued to darken. There was a ring of skin aroundthe edge of the beaker on sample #4 at 24 hours. It is postulated thiswas from the polyethylene in the product. It should be noted that thissample is an improvement over a straight polyethylene film but it is notas good as the straight polycaprolactone film. All of the other samplesappeared like the control (HL-1295 adhesive alone) with no skinning,charring or gelling. Thus, blends with nonbiodegradable polymers arepermissible.

Viscosity Test

Viscosity tests were run, using selected samples from the Beaker Testdescribed above. The mixtures were blended for 5 minutes with aLightening Brand mixer at 350° F.

The following Table shows the viscosity of the molten samples:

                  TABLE VIII                                                      ______________________________________                                        Brookfield viscosity             Vinyl                                        (mPa.s) at 20 rounds   PCL       Acetate and                                  per minute   Adhesive  Adhesion  Adhesive                                     ______________________________________                                        at 325° F.                                                                          3,985     3,895     4,095                                        ______________________________________                                    

As is evident, the PCL does not result in (3% error for viscometer)increased viscosity and thus is compatible. Again, substantial rises inviscosity present a problem in that difficulty in mixing and adhesiveapplication may result from a significant viscosity increase.

Peel Test

In another experiment, the above-mentioned adhesive samples from theviscosity test were coated onto a polyethylene substrate, and theadhesive properties in terms of peeling was determined by adhering thesubstrate onto different materials.

Fine line bonds and spray bonds were made using polyethylene topolyethylene. A simulated diaper application was used and the followingconditions set:

    ______________________________________                                                   Spray        Fine Line                                             ______________________________________                                        Web Speed    500 ft/min.    715 ft/min.                                       Coat Weight  4 mg/in.sup.2  1.4 mg/linear inch                                Nip Pressure 15 psi nip press.                                                                            15 psi                                            Application Temp.                                                                          275° F. App. Temp.                                                                    275° F.                                    ______________________________________                                    

The following results were obtained:

                  TABLE IX                                                        ______________________________________                                        Average Peel Values                                                           (The average of 7-8 samples was taken                                         samples were peeled at 20"/minute)                                                      Packaged (PCL)                                                                           Non-Packaged                                             ______________________________________                                        Fine Line   111 ± 7   102 ± 10                                          Spray        48 ± 2   50 ± 3                                            ______________________________________                                    

Again, it is evident that the packaged adhesives show nearly identicalperformance to the non-packaged adhesive.

Visual Test

In yet another test, A polycaprolactone film of 1 mil. thickness and DSCsoftening point of 60° was used to package HL-1295 adhesive pillows intobags, following the general procedure as described above.

The adhesive-filled bags were placed in a melter/dispenser apparatus andmelted and applied at 275° F. No influence of the packaging materialcomponent in the adhesive was noted in the final product.

While the present invention has been described in connection with theexemplary embodiments thereof, it will be understood that manymodifications will be apparent to those of ordinary skill in the art andthis application is intended to cover any adaptations or variationsthereof.

What is claimed is:
 1. A method of packaging and applying an adhesivecomposition in a biodegradable package, said method comprising the stepsof:(a) providing one substantially uniform separate portion of theadhesive composition; (b) sufficiently solidifying said portion forpackaging; (c) selecting a biodegradable packaging material havingphysical characteristics which are compatible with and do notsubstantially adversely affect the adhesive characteristics of a moltenmixture of said adhesive composition, (d) substantially completelysurrounding said sufficiently solidified portion with a biodegradablepackaging material into a packaged adhesive; and (e) heating saidpackaged adhesive to form a substantially homogeneous mixture andapplying said homogeneous mixture to a substrate, said packagingmaterial having properties such that no degrading of the packagingmaterial occurs upon application.
 2. The method according to claim 1,wherein the packaging material comprises polycaprolactone.
 3. The methodaccording to claim 1, wherein said packaging material comprises a blendof polycaprolactone and a second material, said second material notbeing biodegradable.
 4. The method according to claim 1, wherein thepackaging material is a polymeric net weighing between 0.1 and 5% byweight with respect to the weight of the adhesive composition containedin the package.
 5. The method according to claim 3, wherein thepackaging material is a bag sealed by welding after filling with theadhesive composition.
 6. A method of packaging an adhesive compositionin a biodegradable package, said method comprising the steps of:(a)providing a plurality of substantially uniform separate portions of theadhesive composition; (b) sufficiently solidifying all said portions forpackaging; (c) selecting a biodegradable packaging material havingphysical characteristics which are compatible with and do notsubstantially adversely affect the adhesive characteristics of a moltenmixture of said adhesive composition, (d) forming a batch comprising theplurality of solidified portions; (e) substantially surrounding saidbatch with a biodegradable packaging material; and (f) heating saidpackaged adhesive to form a homogeneous mixture and applying saidhomogeneous mixture to a substrate, said packaging material havingproperties such that no degrading of the packaging material occurs uponapplication.
 7. The method according to claim 6, wherein the packagingmaterial is a polymeric net weighing between 0.1 and 5% by weight withrespect to the weight of the adhesive composition contained in thepackage.
 8. The method according to claim 6, the portions being providedby separating a continuous mass of adhesive composition into roughlypillow-shaped pieces weighing between 0.1 and 50 grams.
 9. The methodaccording to claim 6, wherein the packaging material comprisespolycaprolactone.
 10. The method according to claim 6, wherein saidpackaging material comprises a blend of polycaprolactone and a secondpolymeric material, said second material not being biodegradable. 11.The method according to claim 6, the biodegradable packaging materialhaving a thickness in the range between about 0.5 μm and 10 μm.
 12. Themethod according to claim 6, wherein the biodegradable packagingmaterial is selected from the group consisting of hydrophobic polymerssuch as polylactic acid, polylactides, polycyano acrylate, polyorthoesters, polyanhydrides, polyacetals, polyketals, polyamides, polyesterssuch as polylactic acid, polylactides, water soluble polyvinyl alcohol,bacteria biosynthesized polyester, such as polyhdroxybutyrate,polyhydroxyvalerate, hydrophilic polymers such as poly hydroxy ethylmethacrylate, polyglutamic acid, water soluble polymers such as polyvinyl pyrrolidone, polyacrylamide, poly acrylic acid, poly ethyleneglycol, hydrogels such as cross-linked polymers of HEMA with methoxyethylmethacrylate or methyl methacrylate, water-soluble monomer,cross-linked with water-soluble vinyl monomers, naturally occurringpolymers containing starch and modified starch, cellulose and itsderivatives, cross-linked proteins, syntheticpolypeptides based polymersand gelatin.
 13. A packaged adhesive composition, comprising a batch ofsubstantially uniform separate portion pieces of adhesive composition,said batch being substantially completely surrounded by a biodegradablepackaging material, said packaging material being selected such thatupon heating said batch, said molten packaging material havingproperties such that it does not degrade upon being applied throughapplication equipment.
 14. The composition according to claim 13, theseparate portion pieces being pillow-shaped and weighing between 0.1 and50 grams.
 15. The composition according to claim 13, the biodegradablepackaging further comprising a polymer being selected from the groupconsisting of ethylene based polymers such as ethylene/vinyl acetate,ethylene acrylate, ethylene methacrylate, ethylene methyl acrylate,ethylene methyl methacrylate, high and low density polyethylene,polyethylene blends and chemically modified polyethylene, copolymers ofethylene and 1-6 mono- or di-unsaturated monomers, polyamides,polybutadiene rubber, polyesters such as polyethylene, terephthalate,polybutylene terephthalate; thermoplastic polycarbonates, atacticpoly-alpha-olefins, including atactic polypropylene, and others;thermoplastic polyacrylamide, polyacrylonitrile, copolymers ofacrylonitrile and other monomers such as butadiene styrene, polymethylpentane, polyphenylene sulfide, aromatic polyurethanes,styrene-acrylonitrile, acrylonitrile-butadiene-styrene,styrene-butadiene rubbers, polyethylene terephthalate,acrylonitrile-butadiene-styrene elastomers, polyethylene sulfide, A-B,A-B-A, A-(B-A)n-B, (A-B)_(n) -Y block copolymers wherein the A comprisesa polyvinyl aromatic block, the B block comprises a rubbery midblock,and mixtures of said substances.
 16. The composition according to claim13, wherein the biodegradable packaging material is selected from thegroup consisting of hydrophobic polymers such as polylactic acid,polylactides, polycyano acrylate, polyortho esters, polyanhydrides,polyacetals, polyketals, polyamides, polyesters such as polylacric acid,polylactides, water soluble polyvinyl alcohol, bacteria biosynthesizedpolyester, such as polyhdroxybutyrate, polyhydroxyvalerate, hydrophilicpolymers such as poly hydroxy ethyl methacrylate, polyglutamic acid,water soluble polymers such as poly vinyl pyrrolidone, polyacrylamide,poly acrylic acid, poly ethylene glycol, hydrogels such as cross-linkedpolymers of HEMA with methoxy ethylmethacrylate or methyl methacrylate,water-soluble monomer, cross-linked with water-soluble vinyl monomers,naturally occurring polymers containing starch and modified starch,cellulose and its derivatives, cross-linked proteins,syntheticpolypeptides based polymers and gelatin.
 17. The compositionaccording to claim 13, wherein the packaging material comprisespolycaprolactone.
 18. The composition according to claim 13, whereinsaid packaging material comprises a blend of polycaprolactone and asecond polymeric material, said second material not being biodegradable.